Ibis最新文献

Earlier spring arrival of migratory birds to breeding sites and advanced breeding often bring enhanced reproductive success but demand good body-condition. When populations exhibit extensive winter distributions, the differing energetic costs associated with the quality and migration distance to each wintering area can have implications for individual breeding performance. Using light-level geolocator data from 30 female Common Scoters Melanitta nigra marked at their northeast Iceland breeding site, we explored the extent to which spring migration strategy, arrival and breeding times, and breeding success were related to minimum migration distances from wintering areas to breeding site in multiple years. Because many females produced multiple years of data, we further tested the degree to which individuals used their experience to arrive and breed earlier with increasing age. The females wintered c. 1000–4200 km from the breeding site, yet mostly (87% of 67 tracks) 1000–2000 km away. Increased distance was significantly related to earlier departure from wintering areas (c. 9 days/1000 km), longer stopover time en route and later arrival to breeding sites (c. 6 days/1000 km). Timing of breeding was unrelated to arrival time or migration distance, but significantly advanced with increasing female age (excluding one outlier). Increased migration costs associated with more distant wintering areas do not therefore seem to carry over to affect subsequent timing of breeding despite later arrival, potentially as a consequence of the higher quality of those wintering areas or adequate time after arrival to replenish depleted energy stores. However, further study is needed to elucidate potential effects of breeding time and/or migration distance on breeding success.

Moulting and overwintering Common Scoter Melanitta nigra aggregate in largely undisturbed, shallow-water marine areas, preying upon sessile benthic organisms (mainly bivalves), which do not reproduce during this period of exploitation. Assuming even prey distribution, we predict that Common Scoters would aggregate to moult in shallowest waters with most accessible prey in July, where diving costs were minimal, but would disperse to deeper (i.e. comparatively less profitable) waters through the season as Common Scoter numbers increase and (potentially) as their prey are depleted in winter. To test these hypotheses, we used multiple aerial survey count data to study Common Scoter distribution patterns in Aalborg Bugt, Denmark (in relatively sheltered areas subject to restricted tidal influence), and along the more exposed, highly tidal Schleswig-Holstein North Sea coast in the German Bight. Despite these physical differences, Common Scoters displayed similar distribution patterns in both areas, showing significant increases in mean water depth (from 6.3 m in July to 9.8 m in March in Denmark, 6.5–10.3 m in Germany), number of flock units (432 to 1614; 48 to 581) and the percentage of 3 × 3 km grid squares occupied by birds as the season progressed (15% to 44% of 628 grid cells; 1% to 39% of 408 grid cells). The results support our hypotheses that these consumers distribute themselves to maximize their nutritional and energetic intake, while minimizing costs of gaining food in two contrasting marine environments, but we require sequential sampling of their food supply at differing water depths to confirm the causes of these observed patterns.

Neotropical avian migrants are affected by environmental change throughout their full annual cycles. In the southwestern United States, these species rely on riparian corridors for food and water, for migration stopover sites, and as breeding grounds. Climate change imperils these essential ecosystems, with the southwest predicted to become hotter and more arid, thus resulting in more frequent extreme heat and drought. The tropical forests of Latin America, where many Neotropical migrants overwinter, face similar threats. The impacts of these changes on the demography of migratory riparian species remains poorly understood. We analysed 13 years of capture–mark–recapture bird banding data (2011–2023) from southern Utah to examine the effects of age-class and a range of environmental variables on the survival of a common migratory and riparian breeding bird, the Western Yellow-breasted Chat Icteria virens auricollis. We found that adult chats had a significantly greater probability of survival than first-year birds (mean survival adults: 0.53 ± 0.11; juveniles: 0.12 ± 0.07). While rates of survival differed for the two age-classes, the variability was closely matched across years, indicating that both adults and juveniles are impacted similarly by ecological factors. We also found that annual survival rates were particularly sensitive to the El Niño-Southern Oscillation (ENSO) cycle, with El Niño events being associated with reduced chat survival. This suggests a key negative impact of drier, hotter conditions during migration and on the wintering grounds in Central America—conditions that may become increasingly extreme with future climate change. We also found near-significant negative effects of breeding season heat events (% of days with maximum temperature exceeding the 90th percentile of a 30-year baseline) and spring precipitation, as well as a potential positive association between chat survival and breeding season streamflow. Our results not only demonstrate the importance of environmental variation across the full annual cycle of chats in driving variation in survival, but also highlight how future climate change may impact the demography of a key riparian species.

Hummingbirds play an important role as pollinators and are one of the primary examples of animal–plant coevolution. However, factors such as land-use change, urbanization, exotic species introductions and the disappearance of native plants can negatively affect the persistence of hummingbird populations. Thus, understanding the ecological factors that may favour their presence is essential for their effective conservation in urban areas. We conducted repeated surveys in a native scrubland reserve within Mexico City from 2015 to 2018, and used conditional two-species occupancy models to estimate a species interaction factor, and to analyse the effect of five native plants (Agave salmiana, Echeveria gibbiflora, Opuntia lasiacantha, O. tomentosa and Wigandia urens) and one exotic plant (Leonotis nepetifolia) on the occupancy probability of two hummingbirds: the Broad-billed Hummingbird (Cynanthus latirostris) and the Berylline Hummingbird (Saucerottia beryllina). Considering that both of the hummingbird species could be competing for similar resources, we also tested the effect of the presence of the Berylline Hummingbird on the occupancy of the Broad-billed Hummingbird, assuming its dominance based on larger body-size. We found evidence of positive spatial interactions between plants and hummingbirds, but we did not find these to be consistent throughout the 3 years of monitoring, which could indicate a modification of the original hummingbird–plant interaction networks resulting from urban disturbance. In addition, there were no negative spatial interactions between the two hummingbirds. Instead, we detected an aggregation of both species during two separate seasons, probably owing to one species using the other as a cue for profitable sites. Even though the populations of these two hummingbird species can thrive in an urban ecosystem, changes in spatial interactions might reflect alterations on the structure and functioning of a community. Therefore, we consider it crucial to continue studying their population dynamics and their implications for the conservation of urban hummingbirds.

Bird song is an important and variable sexual signal in many passerine species. One function of this variability may be that males show mate choice and can alter their song according to the quality of the female to which they are singing. If attractive songs are costly, we can hypothesize that males sing more attractively or invest more in singing when trying to attract a better-quality partner. We tested this hypothesis with a field experiment in a wild population of Collared Flycatchers Ficedula albicollis. We presented female stimuli differing in the amount of plumage ornamentation to males on their territory and then recorded their song. We repeated the experiment at least twice for each individual with different female stimuli. We obtained 67 recordings from 29 males, each with 10–50 song responses. Five song traits (song length, mean frequency, frequency bandwidth, tempo and complexity) extracted from the recordings were used in further analyses examining whether the identity of the focal male and the female stimuli explain variance in song traits, and whether males change their songs when exposed to different females. While among-individual variance was considerable in all investigated song traits, female stimuli explained variance only in complexity and tempo. This indicates that males alter these song traits if they sing to different females. We could not clearly identify whether the difference in the response to female stimuli was driven by female quality either at population or individual levels. Overall, our results reveal individuality in song plasticity, and suggest that male mate choice may exist in this species.

GPS tracking has enabled significant advances in the study of animal movements such as migration and habitat use. However, GPS devices can affect the behaviour of tagged individuals, especially for flying animals such as birds, and may ultimately impair their reproduction and/or survival. While numerous studies have investigated the potential negative effects of GPS-tags on birds, few have simultaneously looked at these effects on reproduction and survival, with studies on the latter sometimes suffering from methodological flaws. This study investigated the effects of GPS-tagging on the breeding success and survival of a medium-sized raptor, Bonelli's Eagle Aquila fasciata. Forty-five breeding adults were equipped with backpack-mounted GPS-tags representing 1.2–3.5% of individual body mass. Using a recently developed capture–mark–recapture model that accounts for differences in detectability between types of tags (metal ring, coloured ring or GPS), our results showed no significant differences in survival or breeding success between GPS-tagged and banded individuals. Overall, we did not observe deleterious effects of GPS-tagging on Bonelli's Eagle that would warn against the use of GPS-tags in this species, or other medium-to-large raptors, given the relevant information they might provide for conservation.

The Moroccan population of the globally endangered Great Bustard Otis tarda is close to extinction. Although it is genetically distinct from the Iberian population, no evidence has been previously available to establish the age of its presence in Morocco. A radiocarbon-dated assemblage of Great Bustards from the cemetery cave at Taforalt now confirms the species as a breeding resident of the Maghreb during the Late Pleistocene, ca. 14 700 years before the present. Furthermore, the remains reveal these birds to have been the subject of human exploitation and ritual behaviours. Recognition of the species' ancient status in Morocco reinforces the importance of this isolated and declining population and may help to add impetus to existing conservation efforts.

Passive acoustic monitoring (PAM) efforts have recently been accelerated by the development of automated detection tools, enabling quick and reliable analysis of recordings. However, automated methods are still susceptible to errors, and human processors achieve more accurate results. Our study evaluates the efficacy of three detection methods (auditory, visual and automated using BirdNET) for 43 European bird species (31 diurnal, 12 nocturnal), analysing the impact of various factors on detection probability over different distances. We conducted transmission experiments in two forest types from March to June, examining the effect of call characteristics, weather conditions and habitat features, to assess their impact on detection probability at different distances. Our findings reveal that species detection distance varies with each detection method, with listening to recordings obtaining the highest detectability, followed by the visual method. Although BirdNET is less accurate, it still proves useful for detection, especially for loud species. Large diurnal and small nocturnal species were most detected. Our study emphasizes the importance of considering detection methods to maximize species detectability for effective PAM research.